PILOT 

VISION

Visual Scanning

The probability of spotting a potential collision threat 

increases with the time spent looking outside, but certain 

techniques may be used to increase the effectiveness of 

the scan time. Effective scanning is accomplished with a 

series of short, regularly-spaced eye movements that bring 

successive areas of the sky into the central visual field. Each 

movement should not exceed 10 degrees, and each area 

should be observed for at least 1 second to enable detection. 

Although horizontal eye movements seem preferred by most 

pilots, each pilot should develop a scanning pattern that 

is most comfortable and adhere to it to assure optimum 

scanning. The human eyes tend to focus somewhere, even 

in a featureless sky. If there is nothing specific on which 

to focus, your eyes revert to a relaxed intermediate focal 

distance (10 to 30 feet). This means that you are looking 

without actually seeing anything, which is dangerous. In 

order to be most effective, the pilot should shift glances and 

refocus at intervals. Shifting the area of focus, at regular 

intervals, between the instrument panel and then refocusing 

outside of the aircraft helps to alleviate this problem. [See 

FAA-H-8083-3B and AC 90-48, Pilots’ Role in Collision 

Avoidance.]

Vision Pathophysiology

Cataracts:

A cataract is a painless, progressive condition where the 

lens becomes progressively opaque interfering with vision 

first noted at night and with reading fine print. Most 

cases occur in people over 60 but can occur in younger 

patients with diabetes mellitus, chronic use of cortisone, or 

with a history of eye trauma. Surgical correction involves 

implanting a synthetic intraocular lens, either monofocal or 

multifocal. 

Untreated cataracts were a factor in a fatal accident in 

2013. The FAA permits pilots to fly with early cataracts 

with regular eye examinations and post surgically with 

monofocal lenses when they meet vision standards without 

complications. Multifocal lenses require a brief waiting 

period. The visual effects of cataracts can be successfully 

treated with a 90% improvement in visual function for most 

patients. Regardless of vision correction to 20/20, cataracts 

pose a significant risk to flight safety.

Untreated cataracts were a factor in a fatal accident in 2013. As a 

cataract progresses, it can cause vision disturbances such as glare, 

halos, starbursts, and loss of contrast sensitivity in dark or dusk 

conditions making it difficult for a pilot to land. 

Glaucoma:

Glaucoma can be defined as optic nerve damage resulting 

from an increase in intraocular pressure affecting the ability 

of axons of the retinal ganglion cells to effectively carry visual 

information to the brain.

The specific type of glaucoma, stability on acceptable 

medications, evidence of visual field defects, and adequate 

control of intraocular pressures are factors that influence the 

ability to fly with this condition. Ocular Hypertension or 

Glaucoma Suspect that is monitored and stable or previous 

history of Narrow Angle/Angle Closure Glaucoma which has 

been treated with iridectomy /iridotomy (surgical or laser) 

and is currently stable may be certified for flying. 

Symptoms of severe pain, nausea, transitory loss of 

accommodative power, blurred vision, halos, epiphora 

(excessive watering of the eye), or iridoparesis (swelling of the 

iris of the eye) characteristic of primary or secondary narrow 

angle glaucoma are not acceptable for flying. There must be 

an absence of side effects and unreliable visual fields or other 

defects, and intraocular pressure must be 23 mm Hg or less 

in both eyes to be certified by the FAA.

Heterophoria:

Heterophoria relates to an improper fixation of the visual 

axis, resulting in misalignment of the eyes. When the ability 

to maintain binocular fusion through vergence is exceeded, 

phoria results. A pilot who has such a condition could progress 

to seeing double (tropia) should they be exposed to hypoxia or 

certain medications.

One prism diopter of hyperphoria, six prism diopters of 

esophoria, and six prism diopters of exophoria represent 

FAA phoria (deviation of the eye) standards that may not be 

exceeded.

Color Vision

• Color perception is critical to safe flight for several reasons. 

Within the flight environment many types of information are 

conveyed using color. 

• Human color perception is the result of three types of cones 

that contain variations of the photopigment photopsin that 

are sensitive to long, medium, and short wavelengths. The 

cones are most sensitive to approximately 565nm (red), 

545nm (green), and 440nm (blue), respectively.

• Six to eight percent of males have some degree of genetically 

programmed color blindness.

• There are many degrees of color vision deficiency, including 

perception, that are skewed but largely trichromatic. Some 

individuals are “weak,” or anomalous, in detecting certain 

colors, while others have dichromatic vision and only have 

two cone types.

• An applicant can be tested with a number of different color 

vision tests: the FAA recommends Richmond HRR (Hardy 

Rand and Rittler) pseudoisochromatic plates based on the 

ability to test for both Red-Green and Blue-Yellow color 

deficiency.

Richmond HRR pseudoisochromatic plates can test for Blue – Yellow color deficiency 

(tritanopia)

Monocular Vision

A pilot with one eye (monocular), or with effective visual acuity 

equivalent to monocular (i.e., best corrected distant visual 

acuity in the poorer eye is no better than 20/200), may be 

considered for medical certification through special issuance with 

a satisfactory adaption period, complete evaluation by an eye 

specialist, satisfactory visual acuity corrected to 20/20 or better by 

lenses of no greater power than ±3.5 diopters spherical equivalent, 

and by passing an FAA medical flight test (MFT).

A Word about Contact Lenses

Monovision contact lenses (one contact lens for distant vision 

and the other lens for near vision) make the pilot alternate his/

her vision; that is, a person uses one eye at a time, suppressing 

the other, and consequently impairs binocular vision and depth 

perception. These lenses are not acceptable for piloting an aircraft.

The Eyes Have It

Good near, intermediate, and distant visual acuity is vital because:

• Distant vision is required for VFR operations including takeoff, attitude control, navigation, and landing.

• Distant vision is especially important in avoiding midair 

collisions.

• Near vision is required for checking charts, maps, frequency 

settings, etc.

• Near and intermediate vision are required for checking aircraft 

instruments.

Pilots are encouraged to learn about their own visual strengths and 

weaknesses. Changes in vision may occur imperceptibly or very 

rapidly. Any change in range of visual acuity at near, intermediate, 

and distant points should be brought to the attention of a licensed 

physician or Aviation Medical Examiner (AME). An extra pair of 

corrective lenses or glasses should be carried when flying. Always 

remember vision is a pilot’s most important sense.

See and Be Seen:

• Outside of a 10° cone, visual acuity drops 90%.

• Pilots are 5 times more likely to have a midair collision with an 

aircraft flying in the same direction than with one flying in the 

opposite direction.

• Avoid self-imposed stresses such as self-medication, alcohol 

consumption, smoking, hypoglycemia, sleep deprivation, and 

fatigue.

• Do not use monovision contact lenses while flying an aircraft.

• Use supplemental oxygen during night flights above 5,000 ft 

MSL and daytime flights above 10,000 ft MSL. 

• Any pilot can experience visual illusions–rely on instruments to 

confirm visual perceptions during flight.

Some images used from The Federal Aviation Administration. 

Helicopter Flying Handbook. Oklahoma City, Ok: US Department 

of Transportation; 2012; 13-1. Publication FAA-H-8083. Available 

at: https://www.faa.gov/regulations_policies/handbooks_manuals/

aviation/helicopter_flying_handbook/. Accessed September 28, 2017.

Provided by 

Aerospace Medical Education Division, AAM-400 

To obtain copies of this brochure online:

http://www.faa.gov/pilots/safety/pilotsafetybrochures/

or contact:

Federal Aviation Administration

Civil Aerospace Medical Institute

AAM-400

P.O. Box 25082

Oklahoma City, OK 73125

(405) 954-4831

OK-17-2021 (10-17)

Glare Halo Starburst
PILOT VISION

Vision is a pilot’s most important sense to obtain reference 

information during flight. Most pilots are familiar with the optical 

aspects of the eye. Before we start flying, we know whether we 

have normal uncorrected vision, are farsighted or nearsighted, 

or have other visual problems. Most of us who have prescription 

lenses, contacts, or eyeglasses have learned to carry an extra set of 

glasses with us as a backup when we fly; however, vision in flight is 

far more than a lesson in optics.

Seeing involves the transmission of light energy (images) from the 

exterior surface of the cornea to the interior surface of the retina 

(inside the eye) and the transference of these signals to the brain.

The Anatomy of the Eye

• Light from an object enters the eye through the cornea and then 

continues through the pupil.

• The opening (dilation) and closing (constriction) of the pupil is 

controlled by the iris, which is the colored part of the eye. The 

function of the pupil is similar to that of the diaphragm of a 

photographic camera: to control the amount of light.

• The lens is located behind the pupil and its function is to focus 

light on the surface of the retina.

• The retina is the inner layer of the eyeball that contains 

photosensitive cells called rods and cones. The function of the 

retina is similar to that of the film in a photographic camera: to 

record an image.

• The cones are located in higher concentrations than rods in the 

central area of the retina known as the macula, which measures 

about 4.5 mm in diameter. The exact center of the macula has a 

very small depression called the fovea, which contains cones only. 

The cones are used for day or high-intensity light vision. They are 

involved with central vision to detect detail, perceive color, and 

identify far-away objects.

• The rods are located mainly in the periphery of the retina—an 

area that is about 10,000 times more sensitive to light than the 

fovea. Rods are used for low light intensity or night vision and 

are involved with peripheral vision to detect position references, 

including objects (fixed and moving) in shades of gray, but cannot 

be used to detect detail or to perceive color.

• Light energy (an image) enters the eyes and is transformed by the 

cones and rods into electrical signals that are carried by the optic 

nerve to the posterior area of the brain (occipital lobes). This part 

of the brain interprets the electrical signals and creates a mental 

image of the actual object that was seen by the person.

The Anatomical Blind Spot

The area where the optic nerve connects to the retina in the back of 

each eye is known as the optic disk. There is a total absence of cones 

and rods in this area, and consequently, each eye is completely blind 

in this spot. Under normal binocular vision conditions this is not a 

problem because an object cannot be in the blind spot of both eyes 

at the same time. On the other hand, where the field of vision of 

one eye is obstructed by an object (windshield post), a visual target 

(another aircraft) could fall in the blind spot of the other eye and 

remain undetected.

The Night Blind Spot

The “Night Blind Spot” appears under conditions of low ambient 

illumination due to the absence of rods in the fovea and involves an 

area 5 to 10 degrees wide in the center of the visual field. Therefore, 

if an object is viewed directly at night, it may go undetected or it 

may fade away after initial detection due to the night blind spot.

The Fovea

The fovea is the small depression located in the exact center of 

the macula, which contains a high concentration of cones but no 

rods, and this is where our vision is most sharp. While the normal 

field of vision for each eye is about 135 degrees vertically and 

about 160 degrees horizontally, only the fovea has the ability to 

perceive and send clear, sharply focused visual images to the brain. 

This foveal field of vision represents a small conical area of only 

about 1 degree. To fully appreciate how small a one-degree field is, 

and to demonstrate foveal field, take a quarter from your pocket 

and tape it to a flat piece of glass, such as a window. Now back off 

4 1/2 feet from the mounted quarter and close one eye. The area 

of your field of view covered by the quarter is a one-degree field, 

similar to your foveal vision.

We know that you can see a lot more than just that one-degree 

cone, but do you know how little detail you see outside of that 

foveal cone? For example, outside of a ten-degree cone, concentric 

to the foveal one-degree cone, you see only about one-tenth of 

what you can see within the foveal field. In terms of an oncoming 

aircraft, if you are capable of seeing an aircraft within a pilot 

foveal field at 5,000 feet away, with peripheral vision you would 

detect it at 500 feet. That is why, when you were learning to fly, 

your instructor always told you to “put your head on a swivel,” to 

keep your eyes scanning the wide expanse of space in front of your 

aircraft.

Types of Vision

• Photopic Vision. During daytime or high intensity artificial 

illumination conditions, the eyes rely on central vision (foveal 

cones) to perceive and interpret sharp images and color of 

objects.

• Mesopic Vision. Occurs at dawn, dusk, or under full 

moonlight levels and is characterized by decreasing 

visual acuity and color vision. Under these conditions, a 

combination of central (foveal cones) and peripheral (rods) 

vision is required to maintain appropriate visual performance.

• Scotopic Vision. During nighttime, partial moonlight, or 

low intensity artificial illumination conditions, central vision 

(foveal cones) becomes ineffective to maintain visual acuity 

and color perception. Under these conditions, if you look 

directly at an object for more than a few seconds, the image 

of the object fades away completely (night blind spot). 

Peripheral vision (off center scanning) provides the only 

means of seeing very dim objects in the dark. 

Factors Affecting Vision

• The greater the object size, ambient illumination, contrast, 

viewing time, and atmospheric clarity, the better the visibility 

of such an object.

• During the day, objects can be identified easier at a 

great distance with good detail resolution. At night, the 

identification range of dim objects is limited and the detail 

resolution is poor.

• Surface references or the horizon may become obscured 

by smoke, fog, smog, haze, dust, ice particles, or other 

phenomena, although visibility may be above Visual Flight 

Rule (VFR) minimums. This is especially true at airports 

located adjacent to large bodies of water or sparsely populated 

areas where few, if any, surface references are available. Lack 

of horizon or surface reference is common on over-water 

flights, at night, and in low-visibility conditions.

Flying at night under clear skies with ground lights below can result 

in situations where it is difficult to distinguish the ground lights from 

the stars. A similar problem is encountered during certain daylight 

operations over large bodies of water. Various atmospheric and water 

conditions can create a visual scene with no discernible horizon.

• Excessive ambient illumination, especially from light 

reflected off the canopy, surfaces inside the aircraft, clouds, 

water, snow, and desert terrain can produce glare that 

may cause uncomfortable squinting, eye tearing, and even 

temporary blindness.

• Presence of uncorrected refractive eye disorders such as 

myopia (nearsightedness–impaired focusing of distant 

objects), hyperopia (farsightedness–impaired focusing of 

near objects), astigmatism (impaired focusing of objects in 

different meridians), or presbyopia (impaired focusing of 

near objects). 

• Self-imposed stresses such as self-medication, alcohol 

consumption (including hangover effects), tobacco 

use (including withdrawal), hypoglycemia, and sleep 

deprivation/fatigue can seriously impair your vision.

• Inflight exposure to low barometric pressure without the 

use of supplemental oxygen (above 10,000 ft during the 

day and above 5,000 ft at night) can result in hypoxia, 

which impairs visual performance.

• Other factors that may have an adverse effect on 

visual performance include windscreen haze, improper 

illumination of the cockpit and/or instruments, scratched 

and/or dirty instrumentation, use of cockpit red lighting, 

inadequate cockpit environmental control (temperature 

and humidity), inappropriate sunglasses and/or prescription 

glasses/contact lenses, and sustained visual workload during 

flight.

• Due to the effects of carbon monoxide on the blood, 

smokers may experience a physiological altitude that is 

much higher than actual altitude. The smoker is thus 

more susceptible to hypoxia at lower altitudes than the 

nonsmoker.

Focusing

The natural ability to focus your eyes is critical to flight 

safety. It is important to know that normal eyes may 

require several seconds to refocus when switching views 

between near (reading charts), intermediate (monitoring 

instruments), and distant objects (looking for traffic or 

external visual references).

If dark-adapted eyes are exposed to a bright light source 

(searchlights, landing lights, flares, etc.) for a period in 

excess of 1 second, night vision is temporarily impaired: 

Exposure to aircraft anti-collision lights does not impair 

night vision adaptation because the intermittent flashes 

have a very short duration (less than 1 second).